Post traumatic stress disorder (PTSD) is a condition that develops as a result of exposure to a traumatic event and is characterized by intense physiological and psychological reactivity to stimuli associated with that trauma. PTSD represents a substantial proportion of the burden of illness among Veterans. A recent study found that PTSD was diagnosed in 13% of Veterans returning from Iraq and Afghanistan. Recent reports have also highlighted that PTSD is associated with suicidality - a fact that may explain the alarming rise of suicidal behavior amongst returning Veterans. Several studies suggest that meditation-based treatments may be helpful in treating PTSD. Sudarshan Kriya Yoga (SKY) is a meditation technique that involves a sequence of breathing exercises and has shown promise in treating PTSD. There are several lines of evidence to suggest that such meditation techniques provide a solid foundation for treating PTSD. First, breathing meditation techniques offer a powerful method for balancing autonomic nervous system activity that is often heightened in PTSD. Second, they promote the relaxation response that counters hyperarousal and results in a calmer approach to difficulties and challenges. Third, they may improve sleep quality. This may be important in treating PTSD because memories are encoded into long-term storage during sleep via a process known as consolidation. It is possible that the disturbed sleep which is common in PTSD (nightmares and insomnia) lead to disrupted memory consolidation. Therefore improvement in sleep may lead to improvement in PTSD. Despite promising findings, meditation has not been sufficiently studied in Veterans to recommend its widespread use in treating PTSD. The goal of this proposal is to examine the effects of SKY meditation therapy on Veterans with clinically significant PTSD symptoms. SKY intervention will be compared to cognitive processing therapy (CPT) that is commonly used to treat Veterans with PTSD. CPT will be given as a cognitive only version (CPT-C) which is efficacious in treating PTSD. Veterans will be randomly assigned to one of the two groups (SKY, CPT-C; n=38 per group) and treatment will be delivered over a six-week period. A noninferiority experimental design will be used as is appropriate for trials in which the primary objective is to show that a novel intervention (SKY) is as effective as the standard intervention. Patients' PTSD symptoms will be monitored across time; before treatment (i.e., baseline), at the end of treatment, one month after treatment and 12 months after treatment. Other measures will be taken at baseline and at the end of treatment, and will include autonomic arousal (heart rate) and cognitive functioning including memory consolidation. We will also monitor dropout rates as these can be high in conventional PTSD treatment programs. Based on our preliminary studies using SKY in Veterans with PTSD and the existing literature, we expect that PTSD symptom severity will be reduced following treatment with SKY, that this effect will not be clinically infeior to CPT-C and that the dropout rates will be no higher than CPT-C. Such findings would provide strong evidence for the efficacy of SKY in treating Veterans with PTSD. We also expect that improvements in clinical measures of PTSD will correlate with improvements in memory consolidation, reflecting improvements in sleep following treatment. It is also likely that the individual's response to treatment will be influenced by their baseline characteristics. The SKY and CBT-C interventions focus on different aspects of PTSD; the SKY intervention focuses on breathing and relaxation techniques whereas CPT-C focuses on modifying the understanding of trauma through cognitive restructuring. For this reason the SKY intervention may be more effective for Veterans who have exaggerated arousal (e.g. heightened heart rate). In contrast the CPT-C intervention may be more effective for Veterans who have more cognitive symptoms (e.g., flashbacks, attentional difficulties) since CPT-C addresses cognitive processes. The long term goal of this project is to conduct a fully-powered multi-center randomized controlled clinical trial of SKY meditation in Veterans.